There is precision engineering, and there is having to test fit and going whatever works. No numbers is a strong hint pointing to the second. First one would be implied by X+-Y numbers. Sometimes the plastic is harder, suggesting they use whatever is loaded in the machine. And different materials, different shrinking and flexibility. Magnets can also be wrong, as "make one, label as imperial or metric and blame the +-Y if anyone asks". There are two items in the problem. IMHO, order multiple and use epoxy glue or GS to fill the difference. Bonus: the flexibility should help with shocks and keep the magnet surface level with the table. TL;DR: no strong commitment in the plastic or magnet manufacture, so test and use whatever works at a given time.